Many types of vertical flow meters are now available on the market. FIG. 1 illustrates an example that a vertical flow meter 1 is assembled with an upper flow tube 11 and a lower flow tube 12 for various types of liquids to flow through. The vertical flow meter 1 includes a holding plate 13 installed on the back side thereof with a guide slot 131 formed on the holding plate 13, and a screw fastener 141 run through the guide slot 131 to fasten an induction mechanism 14 to the holding plate 13. When the vertical flow meter 1 is in use, the back side of the vertical flow meter 1 and a wall surface 15 are very close and spaced from each other with only a small gap 16 which makes adjustment of position of the induction mechanism 14 difficult. To do the adjustment of the induction mechanism 14, first, the vertical flow meter 1 has to be detached, and the screw fastener 141 has to be unfastened. After the position of the induction means 14 has been adjusted, the screw fastener 141 has to be fastened again. Hence for the conventional vertical flow meter 1, adjustment of the position of the induction mechanism 14 is very inconvenient and time-consuming. There is still room for improvement.